s390/pci: add locking for fmb access

Function measurement can be toggled at runtime. Make sure that
all access to the fmb is protected via a mutex.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pci.h

@@ -7,6 +7,7 @@
 #define PCI_BAR_COUNT	6
 
 #include <linux/pci.h>
+#include <linux/mutex.h>
 #include <asm-generic/pci.h>
 #include <asm-generic/pci-dma-compat.h>
 #include <asm/pci_clp.h>
@@ -76,6 +77,7 @@ struct zpci_dev {
 	u8		pft;		/* pci function type */
 	u16		domain;
 
+	struct mutex lock;
 	u8 pfip[CLP_PFIP_NR_SEGMENTS];	/* pci function internal path */
 	u32 uid;			/* user defined id */
 	u8 util_str[CLP_UTIL_STR_LEN];	/* utility string */

arch/s390/pci/pci.c

@@ -827,6 +827,7 @@ int zpci_create_device(struct zpci_dev *zdev)
 	if (rc)
 		goto out;
 
+	mutex_init(&zdev->lock);
 	if (zdev->state == ZPCI_FN_STATE_CONFIGURED) {
 		rc = zpci_enable_device(zdev);
 		if (rc)

arch/s390/pci/pci_debug.c

@@ -58,8 +58,12 @@ static int pci_perf_show(struct seq_file *m, void *v)
 
 	if (!zdev)
 		return 0;
-	if (!zdev->fmb)
+
+	mutex_lock(&zdev->lock);
+	if (!zdev->fmb) {
+		mutex_unlock(&zdev->lock);
 		return seq_printf(m, "FMB statistics disabled\n");
+	}
 
 	/* header */
 	seq_printf(m, "FMB @ %p\n", zdev->fmb);
@@ -78,6 +82,7 @@ static int pci_perf_show(struct seq_file *m, void *v)
 				   pci_perf_names[i], *(stat + i));
 
 	pci_sw_counter_show(m);
+	mutex_unlock(&zdev->lock);
 	return 0;
 }
 
@@ -95,19 +100,17 @@ static ssize_t pci_perf_seq_write(struct file *file, const char __user *ubuf,
 	if (rc)
 		return rc;
 
+	mutex_lock(&zdev->lock);
 	switch (val) {
 	case 0:
 		rc = zpci_fmb_disable_device(zdev);
-		if (rc)
-			return rc;
 		break;
 	case 1:
 		rc = zpci_fmb_enable_device(zdev);
-		if (rc)
-			return rc;
 		break;
 	}
-	return count;
+	mutex_unlock(&zdev->lock);
+	return rc ? rc : count;
 }
 
 static int pci_perf_seq_open(struct inode *inode, struct file *filp)